This invention relates to a direct injected engine for an outboard motor and more particularly to an improved cooling arrangement for a direct injection system for a two cycle internal combustion engine.
Two cycle engines are widely used, particularly in applications where high specific outputs and relatively uncomplicated, simple engine constructions are desirable. Thus, two cycle engine are frequently employed as the power plant in an outboard motor because of the small space available in the power head of such engines and the demand for relatively high performance.
However, because of environmental concerns, there is a desire to significantly improve the performance of two cycle engines particularly in the area of exhaust emission control. One particularly advantageous method for reducing unburned hydrocarbons in the exhaust system without sacrificing engine performance is through the use of direct cylinder injection.
Although direct cylinder injection is particularly useful in improving engine performance, there are some substantial difficulties in applying it to certain applications, such as outboard motors. One of these has to do with the fact that an outboard motor is quite compact and there is very little room for the added components required by direct cylinder injection. That is, a conventional fuel injection system of the manifold type includes generally a low pressure pump, a high pressure pump, a pressure regulator and a fuel manifolding system for delivering fuel from the supply system to the fuel injectors. With outboard motor applications because of the confined space, it is also the practice to utilize a fuel vapor separator for ensuring that air or vapors cannot be transmitted to the injectors to cause misinjection.
When direct cylinder injection is employed, the type of delivery system utilized with manifold injectors is not sufficient to generate the pressures required for direct cylinder injection. Therefore, it is necessary to employ an additional high pressure pump which is generally a positive displacement, engine driven pump. Thus, the fuel supply system becomes more complex and more complicated, thus further minimizing the space available.
An added problem presented by direct cylinder injection is that the fuel injectors and their control systems become more complicated and more expensive. Although it is desirable to be able to use automotive components, the fact that the engine may be a two-cycle engine requires more injections in a given time period than with automotive, four-cycle applications. Therefore, the power supply for the operation of the fuel injectors tends to generate more heat. In addition, the control of higher pressures requires higher voltages, sometimes as high as 100 volts, in order to operate the injector valve. Thus, there is obviously generated considerable heat.
Therefore, it is essential that some form of cooling system be available for cooling the components of the electrical control for the fuel injectors. Normally, some form of injector driver circuit is utilized for this purpose, and it is important to cool this injector driver so as to ensure continued efficiency and effectiveness of the electrical driving supply.
It is, therefore, a principle object of this invention to provide an improved electrical cooling arrangement for the fuel injectors of a direct injected outboard motor.
It is a further object of this invention to provide an improved cooling arrangement for cooling the injectors of a direct injected, two-cycle outboard motor.
In addition to the heat issue, the use of the higher electrical voltages and the confined location makes it desirable to maintain short leads and conductors between the components of the electrical supply system. This is also dictated, somewhat, by the compact nature of the outboard motor itself.
It is, therefore, a still further object of this invention to provide an improved and compact electrical system for driving the injectors of an outboard motor wherein the length of electrical conduits and the number of connections can be reduced.
In connection with the mounting and location of the injector drivers for an outboard motor, if the engine is of the V-type, as is commonly utilized with outboard motors, it may be advantageous to mount the injector drivers in the valley between the cylinder banks. With two-cycle engines, on the other hand, the exhaust system for the engine is normally formed by manifolds that are formed integrally in the cylinder block in this area. Thus, considerable heat is present which makes it somewhat undesirable to mount the injector drivers in this otherwise available area.
It is a further object of this invention, therefore, to provide an improved mounting and cooling arrangement for the injector drivers of the V-type engine having exhaust manifolds in the valley between the cylinder banks and wherein there is a cooling system for adequately cooling not only the exhaust system but also the injector drivers so they can be mounted in this location.